solve problem

leet-code/133-clone-graph/README.md

@@ -0,0 +1,28 @@
+# 133-clone-graph
+Given a reference of a node in a connected undirected graph.
+
+Return a deep copy (clone) of the graph.
+
+Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors.
+
+class Node {
+    public int val;
+    public List<Node> neighbors;
+}
+
+
+Test case format:
+
+For simplicity, each node's value is the same as the node's index (1-indexed). For example, the first node with val == 1, the second node with val == 2, and so on. The graph is represented in the test case using an adjacency list.
+
+An adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.
+
+The given node will always be the first node with val = 1. You must return the copy of the given node as a reference to the cloned graph.
+
+Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
+Output: [[2,4],[1,3],[2,4],[1,3]]
+Explanation: There are 4 nodes in the graph.
+1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
+2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
+3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
+4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).

leet-code/133-clone-graph/index.js

@@ -0,0 +1,41 @@
+/**
+ * // Definition for a _Node.
+ * function _Node(val, neighbors) {
+ *    this.val = val === undefined ? 0 : val;
+ *    this.neighbors = neighbors === undefined ? [] : neighbors;
+ * };
+ */
+
+/**
+ * @param {_Node} node
+ * @return {_Node}
+ */
+var cloneGraph = function(node) {
+    // handle edge case
+    if (node === null) return node
+    // keep track of the node to return
+    const start = new Node(node.val)
+    // manage cycle detection by keeping track of which nodes have been visited
+    const map= new Map();
+    // seed the map with the start node
+    map.set(node, start)
+    // keep track of nodes to visit
+    const stack = [node];
+    // exhaust the stack
+    while (stack.length > 0) {
+        const next = stack.pop();
+        // consider each neighbor
+        for (const neighbor of next.neighbors) {
+            // identify nodes that have never been visited
+            if (!map.has(neighbor)) {
+                // record the node as visited
+                map.set(neighbor, new Node(neighbor.val))
+                // schedule the node to be visited
+                stack.push(neighbor)
+            }
+            // update the cloned node's neighbors
+            map.get(next).neighbors.push(map.get(neighbor))
+        }
+    }
+    return start;
+};